Matheus Johann Weiss is Vice Commander and 2nd Company Commander of the 203rd Aerial Mage Battalion, directly appointed by Tanya von Degurechaff after transferring from the Imperial Army's Eastern Army. He possesses a curved face, black hair, and black eyes (occasionally noted as violet). Weiss consistently wears military attire, including his officer suit off-duty and specialized flying gear in combat. He displays prudence without rigidity, excelling at unit management, discipline, and battalion logistics, earning his subordinates' confidence through consistent concern for their welfare. For Tanya, he functions as a reliable and thoughtful subordinate, warranting significant time investment; their interactions range from casual conversation to occasional bickering. Weiss maintains positive relationships with officers like Vooren Grantz and Viktoriya Serebryakov, showing particular consideration for the latter as one of the unit's few women; a documented instance exists of him playfully teasing Serebryakov while intoxicated. His service includes all major 203rd Battalion operations: the annihilation of Dacia, the Osfjord landing, and engagements against the Francois Republic on the Western Front, followed by deployments to North Africa and the Eastern Front against the Russy Federation. Initially, his tactics adhered strictly to doctrine, lacking innovation—evidenced by withdrawal upon encountering Dacian anti-magic formations. Wartime experience gradually fostered increased aggression, impressing Tanya sufficiently to trust him with continuing critical operations like Osfjord if she became incapacitated. Following the battle of Tiegenhof and Kampfgruppe Salamander's formation, he received promotion while retaining his position as Tanya's deputy. In this expanded role, he commands the 203rd during Tanya's absences and coordinates between the regiment's constituent battalions. This coordination initially caused friction with an infantry battalion commander, though tensions resolved after the unit's replacement by elite paratroopers from the imperial capital. His loyalty to Tanya endures despite frequent shock at her statements and actions, rooted in his belief that she prioritizes troop welfare.